Stimulation of Bovicin HC5 Production and Selection of Improved Bacteriocin-Producing Streptococcus equinus HC5 Variants
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Stimulation of Bovicin HC5 Production and Selection of Improved Bacteriocin-Producing Streptococcus equinus HC5 Variants Sofia Magalhães Moreira 1
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Tiago Antônio de Oliveira Mendes 2
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Hilário Cuquetto Mantovani 1
# Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Bovicin HC5 is a peptide that has inhibitory activity against various pathogenic microorganisms and food spoilage bacteria. Aiming to improve the productivity of this bacteriocin, we evaluated several potential factors that could stimulate the synthesis of bovicin HC5 and selected variants of Streptococcus equinus (Streptococcus bovis) HC5 with enhanced bacteriocin production by adaptive laboratory evolution (ALE). The highest production of the bacteriocin (1.5-fold) was observed when Strep. equinus HC5 was cultivated with lactic acid (100 mmol/L). For the ALE experiment, Strep. equinus HC5 cells were subjected to acidshock (pH 3.0 for 2 h) and maintained in continuous culture for approximately 140 generations (40 days) in media with lactic acid (100 mmol/L) and pH-controlled at 5.5 ± 0.2. An adapted variant was selected showing a distinct phenotype (sedimentation, pigmentation) compared with the parental strain. Bacteriocin production increased 2-fold in this adapted Strep. equinus HC5 variant, which appears to be associated with changes in the cell envelope of the adapted variant and enhanced bacteriocin release into the culture media. In addition, the adapted variant showed higher levels of expression of all bovicin HC5 biosynthetic genes compared with the parental strain during the early and late stages of growth. Results presented here indicate that ALE is a promising strategy for selecting strains of lactic acid bacteria with increased production of bacteriocins. Keywords Bacteriocin . Lactic acid bacteria . Adaptive evolution . RT-qPCR . Rumen
Introduction Many lactic acid bacteria (LAB) are capable of producing antimicrobial peptides known as bacteriocins [1–3]. LAB bacteriocins have received great attention from the food and pharmaceutical industries due to their high chemical stability, the variable spectrum of action toward pathogens, low cytotoxicity against mammalian cells, and low likelihood of promoting bacterial resistance [4–6]. Therefore, there is a growing interest in understanding the biosynthesis of these peptides and increasing their yield and purity for industrial applications.
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12602-020-09703-1) contains supplementary material, which is available to authorized users. * Hilário Cuquetto Mantovani [email protected] 1
Departamento de Microbiologia, Universidade Federal de Viçosa, Vicosa, MG 36570-900, Brazil
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Departamento de Bioquímica e Biologia Molecular, Universidade Federal de Viçosa, Vicosa, MG, Brazil
The production of bacteriocins by LAB is often regulated at the transcriptional level and may be induced by different compounds or environmental stimuli. The induction of bacteriocin production by co-cul
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